A solution of hydroxide ions, carbonate ions and/or bicarbonate ions is often required to remove protons from a solution, or buffer the pH of a solution, or precipitate an insoluble hydroxide and/or carbonate and/or bicarbonate from a solution. Conventionally, hydroxide ions can be produced by hydrolyzing a base, e.g., slaking quicklime; or, by electrolyzing a salt solution, e.g., electrolyzing an aqueous sodium chloride solution as in the Chlor-alkali process. Conventionally, carbonate ions or bicarbonate ions can be produced by dissolving carbon dioxide gas in water or by dissolving a soluble carbonate or bicarbonate salt, e.g., sodium bicarbonate, in water.
Although hydrolyzing a base or electrolyzing a salt solution can produce hydroxide ions, the conventional production of hydroxide ions consumes large amounts of energy; the conventional methods also release large amounts of carbon dioxide into the environment. Thus, for example, in producing quicklime, large amounts of fossil fuels are burned to calcine and convert limestone to calcium oxide, with the consequential release of large amounts of carbon dioxide into environment. Similarly, in producing hydroxide ions by the Chlor-alkali process, since typically at least 3V is required across the anode and cathode to drive the reaction, large amounts of energy are utilized. As this energy is derived typically from fossil fuelled power generating plants, this process also causes release of large amounts of carbon dioxide into the environment. Similarly, in producing carbonate ions and bicarbonate ions by dissolving carbon dioxide in aqueous solutions, a significant amount of energy is required to pressurize the gas for improved solubility, with the consequential release of large amounts of carbon dioxide into the environment attributable to the energy used. Thus, an energy efficient production of hydroxide ions, carbonate ions and bicarbonate ions is highly desirable.